Dielectric fluids are fluids that can sustain a steady electric field and act as an electrical insulator. Accordingly, dielectric fluids serve to dissipate heat generated by energizing components and to insulate those components from the equipment enclosure and from other internal parts and devices. Among the properties of a dielectric fluid which affect its ability to function effectively and reliably include flash and fire point, heat capacity, viscosity over a range of temperatures, impulse breakdown strength, gassing tendency, and pour point. Due the varying properties of dielectric fluids, they are often defined by these properties rather than by a specific composition.
Dielectric fluids have traditionally been manufactured from cycloparaffinic base oils, silicone oils, or synthetic organic esters. Mineral oil based dielectric fluids have been extensively used because of their wide availability, low cost, and physical properties; however, mineral oils have relatively low flash and fire points. Polychlorinated bi-phenyls (PCBs) were developed as alternative dielectric fluids. PCBs have excellent dielectric properties and they are far less flammable than mineral oils. Government agencies, at one time, mandated the use of PCBs whenever there was a safety concern related to fluid flammability. Unfortunately PCBs have turned out to be an environmentally hazardous material. Silicone oils and high-molecular weight hydrocarbons currently rank as the most popular choices in applications requiring less flammable fluid. To a much lesser extent, synthetic and natural ester-based fluids and synthetic hydrocarbons are also used.
As the supply of oils traditionally used in dielectric fluids is limited, dielectric fluids are becoming increasingly expensive. Further, commercial demand for such oils may soon exceed their supply.
There has been research into developing processes for making oil compositions useful as an electrical or transformer oil and into oil compositions useful an electrical or transformer oil.
By way of example, EP 0 458 574 B1, U.S. Pat. No. 6,083,889, and JP2001195920 disclose processes for producing formulated transformer oil and oil compositions useful as an electrical or transformer oil.
It is well known in the art to produce synthetic oils and there have been many developmental attempts at producing synthetic oils with high performance characteristics. By way of example, EP 0 776 959 A2, EP 0 668 342 B1, WO 00/014179, WO 00/14183, WO 00/14187, WO 00/14188, WO 01/018156 A1, WO 02/064710 A2, WO 02/070629 A1, WO 02/070630 A1, and WO 02/070631 A2 are directed to synthetic lubricant oil compositions and methods for producing the synthetic lubricant oil compositions.
There remains a need for dielectric fluids having desirable properties, including, high fire point, high flash point, excellent dielectric breakdown, good heat capacity, and excellent impulse breakdown strength. There also remains a need for an abundant and economical source for or an efficient and economical process for producing these dielectric fluids.